ANAT_390_Development_II_DougAllan_2011_LectureNotes

ANAT_390_Development_II_DougAllan_2011_LectureNotes -...

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Unformatted text preview: September 12/2011 Early Development II •  Douglas Allan (doug.allan@ubc.ca) •  Early Development –  Notes and figures on website –  Most images from “Human Embryology” 3rd Ed. (Larsen). Last week: Developmental Concepts and Histology of the Implanted Embryo Today: FormaLon of primary germ layers (gastrulaLon) and nervous system (neurulaLon) Embryonic Period, Weeks 3- 9 Week 3 of development: Gastrulation: the rearrangement of cells into the primary germ layers (mesoderm, endoderm and ectoderm). Neurulation: Formation of the nervous system "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986) FerLlizaLon to GastrulaLon Figure 20-14 Diagram of the process of fertilization, zygote formation, morula and blastocyst development, and implantation Pg.479 Color Textbook of Histology (2nd Ed) Gartner and Hiatt FerLlizaLon to GastrulaLon PrimiLve Streak Hypoblast Epiblast Figure 20-14 Diagram of the process of fertilization, zygote formation, morula and blastocyst development, and implantation Pg.479 Color Textbook of Histology (2nd Ed) Gartner and Hiatt GastrulaLon Classic Model: Sea Urchin GastrulaLon (Do not learn any details on this slide) GastrulaLon –  Human Embryology” 3rd Ed. (Larsen). GastrulaLon –  Human Embryology” 3rd Ed. (Larsen). GastrulaLon Cranial Caudal The Visible Embryo: http://www.visembryo.com/ –  Human Embryology” 3rd Ed. (Larsen). GastrulaLon 0.2 mm Cranial 14- 15 days 0.4 mm Caudal PrimiLve Node PrimiLve Streak PrimiLve Pit The Visible Embryo: http://www.visembryo.com/ 16 days 1- 1.5 mm 17- 19 days GastrulaLon Differen'a'on = specific sets of cells differen'ate to express specific genes Gene Expression Along Primi've Streak: Slug (TF) Slug is a DNA- binding transcripLon factor that regulates gene expression in cells at the primiLve streak – the net effect of this gene expression is loss of adhesion between cells at the primiLve streak and their transformaLon into mesoderm. This transformaLon is termed: epithelial- mesenchymal transformaLon. in situ hybridizaLon to mRNA of the slug gene: in chick Control of cell behavior during vertebrate development by Slug, a zinc finger gene Nieto, et al. Science 6 May 1994: 835- 839. Three primary germ layers established: Trilaminar Embryo Day 16: MigraLon of Mesoderm between epiblast (ectoderm) and endoderm Ectoderm –  Human Embryology” 3rd Ed. (Larsen). Fate of the three Germ Layers The Visible Embryo: http://www.visembryo.com/ NeurulaLon and Somitogenesis Day 17- 18 Day 17 Neural tube (ectodermal) Notochord (mesodermal) Day 20 Day 21 Somite (mesodermal) Notochord emerges before neural tube formaLon (black) Neural Tube (blue) derives from ectoderm, buckles inwards and folds into a tube Mesoderm (orange) separates into a number of specialized structures, including somites FormaLon of neural plate Neural Tissue is iniLally ectodermal – it grows cranially (anteriorly) from the primiLve node. The primiLve node does not really move backwards in embryo, the embryo grows (forward). –  Human Embryology” 3rd Ed. (Larsen). NeurulaLon and Somitogenesis 1- 1.5 mm 17- 19 days 1.5- 2 mm 19- 21 days Neural Plate PrimiLve Node Neural Tube 1.5- 3 mm 21- 23 days NeurulaLon and Somitogenesis Cervical region Neural tube first folds up and somites form at cervical (neck) region. And then proceeds caudally –  Human Embryology” 3rd Ed. (Larsen). Forma'on of the Notochord: prelude to neurula'on Notochord only goes as far cranial as the cervical area à༎ top of spinal column Neurulation- formation of the neural tube. Notochord transplantaLon experiments normal normal extra notochord no notochord Notochord provides a signal (induces) a signal that says ‘this side is ventral’ Bertrand et al (2002) PRONEURAL GENES AND THE SPECIFICATION OF NEURAL CELL TYPES. Nat.Rev.Neuro: 3, 517- 530 Mesoderm starts to differen'ate. Day 17- 18 Somites and notochord are completed. Neural Tube and Somites PaMerning the neural tube Bone morphogeneLc protein (BMP) (produced in blue area and diffuses along blue arrows) Sonic hedgehog (Shh) Produced in red areas and diffuses along red arrows Produces Dorsal and Ventral gradient of morphogens High BMP dorsally, low BMP ventrally Low Shh dorsally, high Shh ventrally PaMerning the neural tube The relaLve amount of BMP and Shh in neural tube cells determines which transcripLon factor gets expressed in that cell. This leads to a grid of different transcripLon factor expression in neural tube TranscripLon factor: binds DNA at specific sequences to turn on/off specific genes in a cell PaMerning the neural tube TranscripLon factor expression domains Dorsal Ventral You do not need to know these details TranscripLon factor: binds DNA at specific sequences to turn on/off specific genes in a cell PaMerning the neural tube Each transcripLon factor domain has progenitor cells that will eventually turn into neurons – each domain will give rise to a specific type of neuron You do not need to know these details Lee and Pfaff (2001) TranscripLonal networks regulaLng neuronal idenLty in the developing spinal cord.Nat.Neur.Suppl: 4, 1183- 1191 ...
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This note was uploaded on 10/24/2011 for the course CHEMISTRY chem taught by Professor David during the Spring '11 term at The University of British Columbia.

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